1. Technical Field
The present invention relates to a liquid ejecting apparatus, a head unit, an integrated circuit device for driving a capacitive load, and a capacitive load driving circuit.
2. Related Art
It is known that a liquid ejecting apparatus such as an ink jet printer which prints an image or a document by ejecting ink uses piezoelectric elements (for example, piezo elements). The piezoelectric elements are provided in correspondence with each of a plurality of nozzles of a head unit, each of the piezoelectric elements is driven in accordance with a drive signal, and thereby a predetermined amount of ink (liquid) is ejected from the nozzles at a predetermined timing, and thus dots are formed. The piezoelectric element is a capacitive load such as a capacitor from the viewpoint of electricity, and thus it is necessary to supply a sufficient current, in order to operate the piezoelectric elements of the respective nozzles.
For this reason, the liquid ejecting apparatus described above has a configuration in which a drive signal amplified by an amplification circuit is supplied to a head unit (ink jet driver) and thereby the piezoelectric element is driven. The amplification circuit uses a method for amplifying a current of an original signal before amplification in a class AB mode or the like, but energy efficiency is poor. Thus, in recent years, a class D amplifier has been proposed (refer to JP-A-2010-114711).
In order to obtain (output waveform becomes highly accurate) high ejection accuracy, a class D amplifier for an ink jet head requires an oscillation frequency (1 MHz to 8 MHz) higher than that of a class D amplifier for audio, by 20 times or more. However, because of the high oscillation frequency, the amplifier has features that are susceptible to various noises. For this reason, the present inventors have found that, in the class D amplifier for an ink jet, component layout in the inside of an IC in which significance to be considered for audio is small is important for reducing noise.